In a world where social media gives businesses more immediate ways to connect with customers, is e-mail marketing still relevant? I think so. In fact, the volume of e-mail marketing messages remained at record-setting levels in June, according to Chad White, research director at marketing company Responsys, and retail e-mail volume will grow about 20 percent this year (vs. more than 16 percent in 2011), thanks to a shift away from old-school direct mail and print.

That makes for a more crowded party. Your e-mails are competing with (literally!) millions of others, which means you must be intentional in your efforts to create messages that truly engage your customers. Here's how.

1. Start with a robust list. This is an obvious point, but it's worth reiterating: Make sure the contacts on your e-mail list actually want your messages. You may be as witty as David Sedaris, but if your audience has already tuned you out, what's the point?

How do you know if your list is stale? Check your open rate. The average is 20 percent, according to the Email Marketing Metrics Benchmark Study released in July by marketing firm Silverpop. If your open rate is significantly less than that, you might have a stale list (or the average for your industry varies significantly from that of others).

Other measures of the health of an e-mail list include click-through rates (how many people took a desired action; i.e., clicked on a link) and conversion rates (how many completed a task in an e-mail message, such as buying a product or signing up for an offer). But the open rate is probably the most telling metric.

2. Freshen things up. Freshen it up by doing something unexpected, suggests DJ Waldow, co-author of The Rebel's Guide to Email Marketing. Segment your list to send a dedicated message to those who haven't opened an e-mail recently, and make the content slightly offbeat--shocking, humorous or whatever fits your brand best. "Whatever you normally do, do the opposite," Waldow says. The idea is to incite reaction and (one would hope) reengagement.

It's tempting to hang on to those unresponsive addresses -- it can be painful to think of purging unengaged recipients. But, as Waldow says, "E-mail marketing works best when you speak to those who really want to hear from you."

3. Use real images. Stock photography is so yesterday -- it's far better to use your own images. Punctuate e-mails with images from your Instagram or Pinterest feeds, or use staff photos. I like the way the Ibex Outdoor Clothing newsletter features company employees as models.

"Imagery doesn't have to be polished to tell the story," Waldow says. "Keep it real, light and fun."

But be aware that too many graphic elements might make it more difficult for your message to render across every e-mail client and on multiple devices.

4. Keep it simple. Kill the buzzwords, corporate jargon and Frankenspeak. Instead, communicate like an actual human--even if what you sell is complicated. Simple terms are more likely to be read, so write clearly, and use the first person.

Make your calls to action simple, too. In fact, make them stupid-obvious. Haven't we all been the recipients of confounding e-mails that make it difficult to tell how to access an offer? "Don't make me search!" Waldow says.

5. Create shareable moments. Outfit your e-mail with social-sharing bling: forward-to-a-friend links and buttons for seamlessly sharing the content on Twitter, Facebook, LinkedIn and Google+. I like the way Boston-based VC firm OpenView Venture Partners places a "tweet this" link after each headline teaser in its weekly newsletter, so readers can share the headline directly from the e-mail (instead of having to click through to the article itself).

Also consider how you can make the e-mail itself more social. At MarketingProfs, we highlight a tweet from a member of our community in our daily newsletter. Such features create a sense of camaraderie and add an element of surprise, Waldow notes, "because you never know if you're going to be featured, so a reader is likely to open to see if today is the lucky day!"